All spell casters gain their abilities through a form of demon possession. So in order to gain magical abilites, PCs must track down and trap demons. Of course there are some pretty powerful demons, if the demon is stronger than the PC, the PC could find themselves subjugated to the Demon's will.
Swords form a bond to their wielder. A symbol on the grip that is absorbed through the user's hand and appears on the back of the hand. Maybe only visible to them or others that have the abilities. Could give unique powers depending on when it happened and what they did to get it. It takes a specially made sword that only few can receive and made by a certain race. Then they must do something really heroic to unleash the swords power. Once unleashed it is theirs till they die then the sword goes dormant again till another accomplishes another feat.